Electronic lens



Aug. 22, 1944. E. RUSKA 2,356,535

ELECTRONIC LENS Filed July 10, 1941 2 Sheets-Sheet L]. Y

,fr zverd o n fE/VST 21/5 04 Aug. 22, 1944. 5 E. RUSKA I 2,356,535

ELECTRONIC LENS I Filed July 10; 1941 2 Sheets-Sheet 2 jnventor: v[IQ/v87 Aus/m Patented Aug. 22, 1944 ELECTRONIQLEN Ernst Ruska,Berlin-'Spandau, Germany; vested in the Alien Property Gustod-ianApplication July 10, 1941, Serial No. 401,781 In Germany August 31, 19404 Claims.

The invention relates to electronic microscopes and more particularlyhas reference to diaphragm means employed therewith. I

It is customary to employ suitably positioned diaphragms or stops forthe purpose of improving the performance and observation of electronicmicroscopes. In some instances, it is desirable to locate such a stop atthe focus of the objective lens on the image side of the lens. Suchpractice has the advantage that a diaphragm positioned at this locationwill not limit the field of View. Where this practice is followed, thediaphragm should be movably adjustable to compensate for a change offocus.

It is the major object of this invention to provide improved diaphragmmeans for use with electronic lens means. Another object of theinvention is to provide a diaphragm which is movable axially of anelectronic microscope. A further object is to provide, in an electronicmicroscope, a diaphragm of the type already mentioned which may be movedby means extending outside of the body portion of the instrument.

In order to'make the invention more clearly understood, there is shownin the accompanying drawings one means for carrying the same intopractical effect.

In the drawings:

Fig. 1 is a sectional view of an electronic microscope.

Fig. 2 is a detail sectional view taken on the line 22 of Fig. 1.

Fig. 3 is a diagrammatic showing of the ray paths of an electronicobjective lens with which the diaphragm of Figs. 1 and 2 is associated.

With particular reference to Figs. 1 and 2, there is shown an electronicmicroscope generally indicated by the reference numeral [5 and having anelectron source or cathode l6, condenser lens I1 and an objective lens20. The latter lens has a winding I and jacket 2 while the condenserlens I! has a winding I8 and jacket l9. Pole shoes 3 and 4 areassociated with the objective lens 20 and pole shoes 2| and 22 with thecondenser lens II. All of the foregoing parts are arranged inconventional manner and the pole shoes of the two lenses are alignedwith each other.

The electronic microscope shown in the drawings is in general similar tothat disclosed in Fig. 5 of my United States Patent 2,272,353, issuedFebruary 10, 1942. The electron rays emitted by the cathode l6, as maybe observed from the ray path indicated by the reference numeral l0, arebrought to a focus by the objective lens 20 at the point 24. It is atthis point that it is desired to locate the diaphragm, such point beingon the image side of the lens and below the suitably supported object 9.To carry out this expedient, use is made of tubular member 6 which isslidable in the pole shoe 4 in a direction axially of the microscope andwhich supports a diaphragm 5 at its end nearest the objective lens H.The diaphragm 5 has the usual aperture and is adapted to be located inthe plane of the focus of the objective lens. Adjusting movement of themember 5 and diaphragm 5 is eifected by a rack and pinion arrangement.

This construction comprises rack teeth 1 provided on the exterior of theslidable tubular member 6 which cooperate with a pinion 8 fixed on theend of a shaft 25 which extends from a rotatably mounted conical plugmember 2%. An extension may be provided in the pole shoe 4 to supportthe plug 26. A second shaft extends exteriorly of the microscope fromthe end of the plug 26 away from the pinion 8 and has an operatingbutton 2! fixed on its free end. Conventional packing means or a glandare employed with the conical plug construction to seal off the interiorof the instrument. It will be apparent from the foregoing that byoperation of the button 21 to cause rotation of the pinion 8, thetubular member 6 and diaphragm 5 may be moved to a, desired positionalong the axis of the microscope so that the diaphragm will be locatedat the focus of the objective.

As shown in Figs. 1 and 3, the rays from the cathode l6 pass through thecondenser lens I! and object 9 and are converged at the focus 25 of thelens 20, in the plane of which the diaphragm 5 is located. The rays passthrough the diaphragm and on divergence may be directed onto afluorescent screen or photographic plate 28 to provide an image llthereon.

From the foregoing, it will be apparent that the aims and objects of theinvention have been accomplished in that a simple structure has beenprovided which includes a movable diaphragm for an electronic device aswell as means for adjusting the diaphragm.

What is claimed is:

1. In an electronic microscope, an objective lens, an objectivediaphragm located on the image side of said lens, and means foradjusting said diaphragm along the axis of the electron beam to positionthe diaphragm at the focus of said lens.

2. An electronic microscope as claimed in claim 1,:wherein the adjustingmeans for the diaphragm is operable without destroying the vacuum in themicroscope.

3. An electronic microscope as claimed in claim 1, wherein the diaphragmis mounted on a holder which is slidable in one of the pole pieces ofthe objective lens.

4. In an electronic microscope having a tubular member through whichanelectron beam is transmitted, 'an objective lens located in saidtubular member and a diaphragm for the lens located in the tubularmember on the image p side of the lens, said beam being transmittedthrough the lens and the diaphragm, the'combination of mean foradjusting said diaphragm along the axis of the electron beam to position1 5 the diaphragm at the focus of the lens comprising support means andsupporting the diaphragm, the support means being located outside of thepath of the electron beam, rack means provided on the support means,pinion means rotatable within said tubular means and in cooperativeengagement with said rack means, and, actuating mean extending withinsaid tubular member and operatively connected to said pinion means forrotating the pinion whereby to adjust the position of the diaphragm tothe focal plane of said lens, said actuating means Ii beingoperable fromthe exterior of said tubular means.

' ERNST RUSKA.

